Elliptic Fourier Analysis Research Articles

Outline shape analysis of penguin humeri: a robust approach to taxonomic classification

Humeri have been useful bones in taxonomic determinations of extinct penguins. In the context of neontological taxonomic studies, however, their potential remains unsatisfactorily explored. Here, the variation of the overall closed-outline shape of 60 humeri, assignable to five genera of extant penguins, was investigated. A set of normalized outlines was quantified via elliptical Fourier analysis and subjected to linear discriminant analysis on principal component scores extracted from harmonic coefficients. These geometric representations proved to be a source of easily extractable genus-level taxonomic information. The constructed model provided meaningful discrimination between taxa: the first two linear discriminants captured almost 90% of between-group variance. A cross-validation method based on jackknifing yielded 93% correct identifications, and statistically significant differences between group centroids were also detected (multivariate analysis of variance, p < 0.05). Predictions of genus membership for the intentionally noisy test data (20 outlines) were accurate in 80% of cases.

Two evolutionary units on the South American razor clam Ensis macha (Bivalvia: Pharidae): genetic and morphometric evidence

The patterns of genetic and phenotypic diversity in marine life are the result of different geological and ecological processes. We analyzed the pattern of genetic and morphometric variation of the razor clam Ensis macha along its entire geographic distribution. This species is one of the most important shellfish resources of South America. To uncover the genetic variation across this species, we used sequences of the COI mitochondrial gene and of 856 nuclear orthologs. To describe morphological variation in the shape of the shell, we used elliptic Fourier analysis followed by multivariate statistics. Two main genetic lineages were found, designated as Northern and Southern clades. This genetic distinction is concordant with a biogeographic transition along the Pacific coast of Southern South America, which is also known for other taxa. Based on the genetic distance between the two lineages, each lineage can be considered an incipient species. Morphological approaches revealed similar results, though there was no strict concordance between the morphometric and the genetic results. Geological history and ecological processes could both be responsible for the variation across the range of E. macha. In particular, fragmentation and isolation between populations may have favored genetic diversification, while the environment may have molded the variation shell shape. Lastly, our results have important implications for fisheries management, to preserve biological diversity of the world’s southernmost razor clam species.

Outline analysis of sex and population variation in greater sciatic notch and obturator foramen morphology with implications for sex estimation

The pelvis is known to be the most sexually dimorphic part of the adult human skeleton. Many pelvic sex traits, however, are difficult to analyze quantitatively, with practitioners relying on subjective qualitative descriptions. This study uses elliptical Fourier analysis to explore sexual dimorphism and population variation in two pelvic traits, greater sciatic notch (GSN) and obturator foramen (OF), in a diverse set of 329 ossa coxae. The resultant shape variables support the qualitative descriptions of sex differences. Discriminant function analyses on GSN variables reveal correct classifications over 80% for all sample subsets and 86.8% on the pooled sample; although significant population differences were noted with possible secular changes. Females display more notch variation than males, and age was not a significant factor. OF results were more variable and classification rates were not consistently high enough for use in forensic practice. Furthermore, GSN and OF shape are not significantly correlated.

Species specificity and sexual dimorphism in tooth shape among the three sympatric haplochromine species in Lake Kivu cichlids.

Tooth shape is used to differentiate between morphologically similar species of vertebrates, including fish. This study aimed to quantify tooth shape of three sympatric species: Haplochromis kamiranzovu, H. insidiae, and H. astatodon endemic to Lake Kivu, whose existing identification criteria are currently only qualitative. A quantitative tooth shape analysis was performed based on digitized tooth outline data with a subsequent elliptic Fourier analysis to test for differences among the three species. We looked at crown shape and size differences within H. kamiranzovu and H. insidiae at geographical, habitat, and gender levels. No comparison at habitat level was done for H. astatodon because it is found only in littoral zone. The analysis revealed significant tooth shape differences among the three species. Haplochromis astatodon had a significantly longer major cusp height and a longer and larger minor cusp than that of H. insidiae. It had also a longer major cusp height and a longer and larger minor cusp than that of H. kamiranzovu. Tooth shape differences of H. kamiranzovu and H. insidiae species were not significantly different between littoral and pelagic fish (p > .05) while differences were significant between southern and northern Lake Kivu populations (p < .05). Tooth sizes in H. kamiranzovu and H. insidiae were significantly different, both in height and width as well as in their ratios, and this was true at sex and geographic levels (p < .05), but not at habitat level (p > .05). Tooth shape was also significantly different with sharp teeth for males compared with females of southern populations versus northern ones. These shape‐ and size‐related differences between sexes suggest differences in the foraging strategies toward available food resources in the lake habitat. Further research should explain the genetic basis of the observed pattern.

The Middle Pleistocene hominin mandible from Payre (Ardèche, France)

Although Neandertals are the best-known fossil hominins, the tempo and evolutionary processes in their lineage are strongly debated. This is in part due to the scarcity of the fossil record, in particular before the marine isotopic stage (MIS) 5. In 2010, a partial hominin mandible was discovered at the Middle Paleolithic site of Payre (France) in a layer that is dated to the end of MIS 8/beginning of MIS 7, a time period for which very few fossils are known in Europe. The Payre 15 mandible retains the complete symphyseal region and right lateral corpus with heavily worn P4, M1, and M2 in situ. Taphonomic modifications in the form of three notches suggest that this individual was chewed by a carnivore. We provide here the first detailed description of this specimen and a comparative analysis that includes morphological features, linear mandibular dimensions, an elliptic Fourier analysis of the symphysis, and a morphometric analysis of the M1 roots (based on segmented CT scan data). Our comparative sample encompasses European Middle and Upper Pleistocene specimens attributed to Homo heidelbergensis and Homo neanderthalensis, Upper Pleistocene Homo sapiens, and Holocene Homo sapiens. The Payre 15 mandible shows a combination of primitive and Neandertal-like features, with a receding symphyseal profile without any element of the mentum osseum, a posterior location of the mental foramen and lateral prominence. Its mandibular body is tall and thick anteriorly. Payre 15 has mesotaurodont M1 roots and a three-rooted M2. By its dimensions and combination of features, Payre 15 aligns better with Middle Pleistocene European hominins than with MIS 6–3 Neandertals. Noteworthy, it falls well within the range of variation of the Sima de los Huesos sample. Our results underscore that the total pattern of Neandertal-derived morphology was not achieved at the beginning of the MIS 7 and suggest a low level of mandibular diachronic changes for the period MIS 11–7.

High-throughput gene screen reveals modulators of nuclear shape.

Irregular nuclear shapes characterized by blebs, lobules, micronuclei, or invaginations are hallmarks of many cancers and human pathologies. Despite the correlation between abnormal nuclear shape and human pathologies, the mechanism by which the cancer nucleus becomes misshapen is not fully understood. Motivated by recent evidence that modifying chromatin condensation can change nuclear morphology, we conducted a high-throughput RNAi screen to identify epigenetic regulators that are required to maintain normal nuclear shape in human breast epithelial MCF-10A cells. We silenced 608 genes in parallel using an epigenetics siRNA library and used an unbiased Fourier analysis approach to quantify nuclear contour irregularity from fluorescent images captured on a high-content microscope. Using this quantitative approach, which we validated with confocal microscopy, we significantly expand the list of epigenetic regulators that impact nuclear morphology.

Applied anatomic and phylogenetic considerations of surgical and regional nerve block landmarks on the skull and mandibles of two hystricomorphs; the crested porcupine (Hystrix cristata) and greater cane rat (Thryonomys swinderianus)

This investigation seeks to discriminate variations in anatomic landmarks of regional nerve block/surgical importance in skulls of two phylogenetically related laboratory species; the Old-world porcupines (H. cristata) and Cane rat (T. swinderianus), and comparedfrontal sinus shape outline architecture in mid-sagittal section for both. Using Generalized Procrustes Analysis, the study utilized thirty-seven and forty-eight skull samples of each respectively. for landmarks assessments in right lateral, ventral and right lateral hemi-mandibular views, and Elliptical Fourier analyses for frontal sinus contours. Extremely significant (P ≤ 0.0001) interspecies landmark size variations were observed with Mahalanobis distance of 1.89, 2.03 and 2.06 for the evaluated positions respectively, mean centroid size ranged from 3200 mm in H. cristata to 1400 in T. swinderianus. Shape regression model suggested similar allometric pattern except in mandibles (λ Wilks 0.96, F 44.55) but (λ Wilks 0.88, F 127.9) between species. EFA descriptors demonstrated. amplitude associated attenuations in harmonic values (factor about 1/8 to 1/22,000) with angular orientation in major axes values reduced by not more than ¼ after size normalization. PC1 & 2 contributed 81.19%, 6.29% but 100% in within and between species analysis. Stepwise harmonic increments outline reconstructions demonstrated disparities up to the 6th harmonics with marginally lower variance value in cane rats (1.37) than in porcupines (1.68). The results conclude that skull shape and size disparities observed suggest despite similar phylogeny both are diverse and does not compare in structural and frontal sinus outline shapes.

Assessing Inter‐ and Intra‐reliability in Frontal Sinus Outlines

Human frontal sinuses are highly variable between individuals in terms of their size and shape. This idiosyncratic variation has been used in medicolegal fields for positive identification. Although qualitative comparisons are common practice, several 2D and 3D methods to objectively quantify their morphology have been proposed to statistically support such identifications. One approach has been to outline the superior border of the frontal sinus from traditional radiographs, using Elliptical Fourier analyses (EFA) of those frontal sinus outlines (FSOs) to characterize sinus shape. Several studies show this method quantitatively illustrates FSO uniqueness. To make such a method applicable to medicolegal cases, however, inter‐ and intra‐observer reliability in the tracing of FSOs must first continue to be evaluated.This study uses digital radiographs of 40 crania in Caldwell position from Des Moines University’s anatomical collection to assess inter‐ and intra‐observer variations in FSO tracings. Five crania had bilateral aplasia; two were too difficult to see. FSOs were traced in the remaining 33 crania by two researchers using ImageJ, with the superior orbital border demarcating the inferior boundary. FSOs were imported into SHAPE‐software, and underwent EFA (20 harmonics) and principal component analyses (PCA). PC1 (50.34% of the variance) reflected height‐vs‐breadth relationships, while PC2 (13.40%) reflected differences in outline complexity between researchers; ANOVAs confirmed these significant differences along PC2 (F=10.879; p&lt;0.0001). Further investigation revealed that one observer tended to follow the lobe contours more detailed, tracing further into the septa between lobes. With this knowledge, a second set of tracings by the same researchers, both better accounting for complexity, were undertaken to assess whether more specific instructions can control for such deviations. Subsequent PCAs and ANOVAs indicated no significant differences in PC1 or PC2 within or between individual tracings (p‐values &gt; 0.05). However, several FSO‐tracings still plotted relatively far apart along the PC1 and PC2 axes. These “problematic” sinuses were often smaller in size or had smaller lobes. Interestingly, the issue lies primarily with inferior border placement— not the sinus itself. In such cases, small lobes near the inferior boundary were not always included in the FSO‐tracing, greatly altering FS size and shape as captured by EFA.This information helps support the use of FSOs in forensic identification, but only when appropriate considerations are made. Similar to previous studies, these results indicate that investigators should be aware that FSOs of smaller sinuses may not be as reliable; this study also indicates large sinuses with smaller lobes may also be problematic. Intra‐ and inter‐observer reliability of the placement of the superior orbital border and potential errors beyond tracing deviations need further investigation to fully understand potential errors and any major implications in the use of FSO in medicolegal identifications, given the high stakes of misidentifying an individual or erroneously excluding a true identity.Support or Funding InformationFunding support provided by IOER‐Grant 03‐19‐01.

Ontogenetic Trends in Frontal Sinus Shape

Adult frontal sinus morphology has been studied in biological anthropology, both in terms of its function and variation. Overall, this structure is known to be highly variable among individuals, to such an extent that it is used to make positive identifications in the medicolegal setting. However, very little is known about the growth and developmental processes leading to the wide ranges of frontal sinus size and shape. Although several studies investigate frontal sinus ontogeny in terms of size and linear dimensions, much less is known regarding the ontogeny of its shape. This study partially addresses this gap by examining frontal sinus outlines using longitudinal radiographic data to evaluate when the frontal sinus attains its adult shape.Longitudinal radiographs for 107 individuals (57M/50F) spanning 5–29 years of age (yoa) were obtained from the AAOF Craniofacial Growth Legacy Collection ( www.aaoflegacycollection.org). Superior borders of frontal sinus outlines were digitally traced in ImageJ; the superior orbital border demarcated inferior sinus boundaries. Age of first appearance was also recorded. A total of 749 outlines were imported into SHAPE‐software, where elliptical Fourier (20 harmonics) and principal components (PC) analyses were conducted. PC1 (49.18% variation explained) reflects height‐to‐breadth relationships, while PC2 (11.74%) reflects asymmetry in right versus left lobe dominance.To assess when the frontal sinus attains its adult shape, Euclidean distances of PCs 1–9 (91.58% cumulative variance) between each age point and the 18‐year point were calculated within individuals; this process was repeated for the 20‐year point. Scatterplots with Loess curves for each distance plotted against age suggest adult shape is attained around 20yoa. Sexual dimorphic trends are evident in the Loess curves, whereby males exhibit greater distances from 20yoa at early ages. An analysis of variance confirms these sex‐based differences (F=7.063, P&lt;0.0001); Tukey post‐hocs further suggest that while adult females are not significantly different in shape from adult males or younger females/males (13–19yoa), adult males are significantly different from males 15yoa and younger. T‐tests failed to find significant sex‐based differences for age‐of‐first‐appearance (t=1.482, P=0.142) and adult‐shape (PC1: t=−0.670, P=0.505; PC2: t=1.827, P=0.058). Thus, it appears that while both sexes display similar start times in sinus development and reach similar adult‐shapes, females attain their adult shape sooner. This suggests a slower developmental process in males. Additional studies are needed to determine how these ontogenetic patterns in 2D sinus‐shape relate to the overall size and 3D dimensions of the sinus.

Recognising mollusc shell contours with enlarged spines: Wavelet vs Elliptic Fourier analyses

Gastropod shells may present large spines and sharp shapes that vary according to environmental, taxonomic, and evolutionary factors. In these cases, classic morphometric methods used to study shell contour might not provide a clear representation of morphological shell based on angular decomposition of contour. The present study analyzed and compared for the first time the robustness of the contour analysis using wavelet transformed and Elliptic Fourier descriptors for gastropod shells including enlarged spines. For that, we analyzed two geographical and ecological separated populations of Bolinus brandaris from the NW Mediterranean Sea. Results showed that contour analysis of gastropod shells with enlarged spines can be analyzed using both methodologies, but the wavelet analysis provided a better local discrimination. From an ecological perspective, shells with spines of different sizes were observed in both localities suggesting a wide plasticity of the species.

Using morphometrics to reappraise old collections: The study case of the Congo Basin Middle Stone Age bifacial industry

Despite its strategic location within the continent, Central Africa is rarely integrated into the reconstruction of population dynamics during the Middle Stone Age (MSA) of Africa, especially in terms of the emergence, diffusion and behavioural patterns of Homo sapiens. However, hundreds of sites have been discovered in Central Africa during the 20th century and attributed to the Lupemban, one of the main MSA technological complexes of the region. This complex is mainly characterised by typological criteria based on the numerous bifacial pieces found in the Congo Basin and interpreted as an adaption to the rainforest environment. Most of these Lupemban assemblages have not been studied for decades and thus it is particularly difficult to assess their diversity. This paper presents a detailed combined morphometrical approach (linear measurements and indices, Log Shape Ratio, Elliptic Fourier Analysis) to take a fresh and rigorous look at the Lupemban bifacial tools. We discuss the comparison of different morphometrical approaches to deal with “old” collections for which contexts, particularly chronological ones, are partially missing. We present the results of this approach on three assemblages of bifacial pieces gathered in the 1930s and late 1960s. We quantify their variability and discuss not only their homogeneity but also the variation of a Lupemban hallmark, namely the “Lupemban point”.

Morphometrical methods as tools for identifying field maple (Acer campestre L.) trees

Several morphometrical methods were evaluated with the purpose of distinguishing individual maple trees by their samaras and to reveal shape trends. Landmarks for geometric morphometrics gave 97–98% correctly classified trees in a jackknifed confusion matrix from discriminant analysis, fan‐positioned landmarks and semilandmarks 92%, linear data 79% and elliptic Fourier analysis 65% correctly classified trees. Several principal component analyses (PCA) where conducted revealing shape trends in the investigated samaras. The linear data revealed change in length and the geometric and Fourier data change in the direction of the samara wing. MANOVA and NPMANOVA revealed significant differences between several group means. The results suggest that: 1) landmarks may be an adequate method for distinguishing different individuals of maples 2) the main shape change concerns the direction of the samara wing, which may be horizontal, curved upwards or downwards.

Variation of Otolith Structure in Amur Sleeper Perccottus glenii (Odontobutidae) Populations from Central Russia

Development of annual increments on the otoliths (sagittae) of Amur sleeper Perccottus glenii, as well as the sagitta shape and bilateral asymmetry, is analyzed in the populations from four water bodies of Central Russia: (1) the lake near Maslovka village (Nizhny Novgorod oblast), (2) Sima Pit, (3) Upper Sharapovskii Pit, and (4) Lower Sharapovskii Pit (Moscow oblast). The diameter (along the dorsoventral axis) of the first annual zone is 0.8–1.5 mm. The highest growth rate (29 mm per year on average) and the largest individuals (up to 245 mm TL) are registered in population one. Based on two sagitta shape indices (height to length ratio and ellipticity), a directed bilateral asymmetry is observed in population one. Based on the variation of fluctuated asymmetry, distinct differences between the populations are absent. The elliptic Fourier analysis shows that population one differs from populations two, three, and four in sagitta shape. A small interpopulation variation of sagitta morphology is revealed.

An objective method of shape descriptor state establishment using elliptic Fourier analysis (EFA)

AbstractThis research attempts to systematically establish shape descriptor states through elliptic Fourier analysis (EFA) using pili (Canarium ovatum Engl.) kernel as a model. Kernel images of 53 pili accessions from the National Plant Genetic Resources Laboratory (NPGRL), University of the Philippines Los Baños were acquired using VideometerLab 3. Shape features, such as roundness, compactness and elongation, were extracted from the images. Shapes outlines were characterized using elliptic Fourier coefficients calculated from SHAPE version 1.3 software. Principal component analysis and cluster analysis were used to elucidate clusters representing the shape descriptor states. The first principal component accounts for the variation in length to width ratio; whereas, the second and third principal components explain the variation in the location of the widest portion and the truncation of the apex and base of the kernel, respectively. Cluster analysis separated the different accessions into six distinct clusters at 0.04 Euclidian distance. Six descriptor states, narrowly elliptic, elliptic, widely elliptic, ovate, obovate and lance-ovate, were characterized from the shape outlines and visualized through R's shape on r package. The discrimination between clusters was validated through MANOVA and LDA with 95% correct classification. The Fourier coefficients were also able to represent the variation observed from the physical properties of shape. The method may be used in establishing shape descriptors of all plant parts of all crop species.

Phenotypic selection by kelp gulls against pear-shaped shells of the Antarctic limpet Nacella concinna

Abstract The Antarctic limpet (Nacella concinna) presents two ecotypes related to different water depths: littoral individuals have a robust and taller shell while sublittoral individuals are thinner and flatter. Among the environmental factors possibly causing this divergence, avian predation upon littoral individuals has been mooted but has received little research attention. The kelp gull (Larus dominicanus) is the principal consumer of littoral limpets in the study area. We used shells from littoral and sublittoral zones, and from gull middens to examine – through linear morphometrics and elliptic Fourier analysis – whether selective predation exists, and to evaluate the mode of selection that could be operating on different traits. We found that limpet individuals with the apex displaced towards the anterior side were more likely to be predated. However, a remarkable result was that gulls select dorsal pear-shaped rather than elliptical shells and that there is a directional selection against pear-shaped limpets. However, in contrast to previous studies, we did not find that the proportions of elliptical or pear-shaped individuals differed between the littoral and sublittoral zones. This discrepancy could be related to variations in predatory intensity in different locations. These results suggest that where gulls have a strong influence, their effect could be a key factor in dorsal differentiation in limpet shells.

An analysis of the effect of tooth wear on bovid identification

Previous research provides a method for reducing the subjectivity in taxonomic identification of species in the family Bovidae by quantifying the occlusal surface of molar teeth using elliptical Fourier analysis. In this current study, we specifically test what effect medium to late tooth wear has on the identification of bovids when using the form (size and shape) of the occlusal surface to classify specimens. To achieve this, the classification results of teeth with ≥85% of their occlusal surface (training data set) were compared with the results of teeth with &lt;85% of their occlusal surface (test data set) due to wear. In the training data set, all tribes classified correctly &gt;87% of the time with both Alcelaphini and Reduncini classifying correctly &gt;90% of the time. The worn teeth in the test data set classified correctly at lower rates, but all tribes still collectively had a good classification accuracy (&gt;60%) with classification of Alcelaphini and Tragelaphini at &gt;75% and Reduncini at &gt;65%. Hippotragini classified correctly 50% of the time and Neotragini 42%. The one worn Bovini tooth in the test data set was classified as that of a Hippotragini. The classification rates of teeth with medium to late wear were lower than the unworn teeth, but not so low as to suggest that this methodology for identifying bovid teeth is inappropriate for worn teeth, especially when supplementary to other methods.&#x0D; Significance:&#x0D; &#x0D; Worn teeth can be taxonomically identified by performing elliptical Fourier analysis on the occlusal surface of their teeth.&#x0D; While teeth with medium to late wear correctly classify at lower rates than relatively unworn ones, the methodology is a valuable supplement to other methods for taxonomically identifying bovid teeth. Worn teeth of the tribes Alcelaphini and Tragelaphini classify at the highest rates.&#x0D; &#x0D; Open data set: &#x0D; https://github.com/gjm112/TeethWear

A Multi-Objective Evolutionary Algorithm Model for Product Form Design Based on Improved SPEA2

As a Kansei engineering design expert system, the product form design multi-objective evolutionary algorithm model (PFDMOEAM) contains various methods. Among them, the multi-objective evolutionary algorithm (MOEA) is the key to determine the performance of the model. Due to the deficiency of MOEA, the traditional PFDMOEAM has limited innovation and application value for designers. In this paper, we propose a novel PFDMOEAM with an improved strength Pareto evolutionary algorithm 2 (ISPEA2) as the core and combining the elliptic Fourier analysis (EFA) and the entropy weight and technique for order preference by similarity to ideal solution (entropy-TOPSIS) methods. Based on the improvement of the original operators in SPEA2 and the introduction of a new operator, ISPEA2 outperforms SPEA2 in convergence and diversity simultaneously. The proposed model takes full advantage of this superiority, and further combines the EFA method’s high accuracy and degree of multi-method integration, as well as the entropy-TOPSIS method’s good objectivity and operability, so it has excellent comprehensive performance and innovative application value. The feasibility and effectiveness of the model are verified by a case study of a car form design. The simulation system of the model is developed, and the simulation results demonstrate that the model can provide a universal and effective tool for designers to carry out multi-objective evolutionary design of product form.

Assumption-Free Assessment of Corpus Callosum Shape: Benchmarking and Application

Shape analysis provides a unique insight into biological processes. This paper evaluates the properties, performance, and utility of elliptical Fourier (eFourier) analysis to operationalise global shape, focussing on the human corpus callosum. 8000 simulated corpus callosum contours were generated, systematically varying in terms of global shape (midbody arch, splenium size), local complexity (surface smoothness), and nonshape characteristics (e.g., rotation). 2088 real corpus callosum contours were manually traced from the PATH study. Performance of eFourier was benchmarked in terms of its capacity to capture and then reconstruct shape and systematically operationalise that shape via principal components analysis. We also compared the predictive performance of corpus callosum volume, position in Procrustes-aligned Landmark tangent space, and position in eFourier n-dimensional shape space in relation to the Symbol Digit Modalities Test. Jaccard index for original vs. reconstructed from eFourier shapes was excellent (M=0.98). The combination of eFourier and PCA performed particularly well in reconstructing known n-dimensional shape space but was disrupted by the inclusion of local shape manipulations. For the case study, volume, eFourier, and landmark measures were all correlated. Mixed effect model results indicated all methods detected similar features, but eFourier estimates were most predictive, and of the two shape operationalization techniques had the least error and better model fit. Elliptical Fourier analysis, particularly in combination with principal component analysis, is a powerful, assumption-free and intuitive method of quantifying global shape of the corpus callosum and shows great promise for shape analysis in neuroimaging more broadly.

A new thylacocephalan crustacean from the Upper Jurassic lithographic limestones of southern Germany and the diversity of Thylacocephala

Thylacocephala is a group of extinct eucrustaceans of presumably predatory nature. We describe here a new genus and species of thylacocephalan crustaceans from the Upper Jurassic Solnhofen limestones of Eichstatt (Altmuhltal Formation), Falcatacaris bastelbergeri n. g. n. sp. (about 150 million years old). Falcatacaris bastelbergeri n. g. n. sp. is the fourth species of Thylacocephala found in these deposits. The species differs significantly from other thylacocephalans, especially by characters of the shield. The shield of the specimen is rather low (short in dorsoventral extent) and it bears a long rostrum but no elongated posterior spine. For comparative purposes, we provide an overview of the shield morphology of known thylacocephalan species from literature as well as a morphological analysis of the group. An elliptic Fourier analysis is used to compare the different shield shapes of thylacocephalans to each other; results are presented in PCA plots. Shield length and anterior or posterior shield extensions are the characters with the most variation in thylacocephalan shield morphology.

Deciphering the roles of environment and development in the evolution of a Late Triassic assemblage of conodont elements

AbstractTo assess evolutionary processes in deep time, it is essential to understand the roles of development and environment, both recorded through the morphological variability of fossil assemblages. Thanks to their great abundance and the high temporal resolution of their fossil record, conodont elements are ideal to address this issue. In this paper, we present the first quantitative study of a Carnian–Norian (Late Triassic) assemblage of closely related P1 conodont elements. Using geometric morphometrics (landmarks, sliding landmarks, and elliptic Fourier analysis), we explore the main axes of phenotypic variation and relate them to classically used taxonomic characters. We show that some important taxonomic features follow laws of covariation, hence highlighting developmental constraints. Furthermore, the intraspecific variation within all considered species, either Carnian or Norian forms, is similarly restricted, emphasizing, for the first time in conodont P1 elements, a common line of least resistance to evolution, which means that similar intrinsic (developmental) factors were acting on these taxa and likely biased the evolutionary trajectories of all these taxa in a similar way. Because the evolution between Carnian and Norian forms is known to have followed a trajectory that is significantly different from the line of least resistance, strong extrinsic pressures, such as environmental disturbances, were probably at play around the Carnian/Norian boundary to counteract the effects of these intrinsic, developmental constraints.